Device for opening, in particular, scissor-type jack mechanism

Abstract

A device for opening a scissor-type jack with paired cross-bars, the device having a chamber of variable volume connected to fluid inlet and outlet provided by end plates to which two cover plates are fixed. The first cover plate has two flanges disposed on the opposite sides of the cover plate and extending to a second cover plate and are connected for rotation of the first cover plate to the cross-bars. The second cover plate has two flanges. The distance between the two flanges is smaller than the distance between the flanges of the first cover plate and the flanges of the first cover plate are coaxially connected for rotation to the inside surface of the outer cross-bars, while the flanges of the second cover plate are coaxially connected for rotation to the inside surface of the inside cross-bars. In this way the axis of the rotary connection of the two cover plates to the cross-bars, intersects a line joining the centroids of the two end plates.

I claim: 
     
       1. A scissor-type jack mechanism, in particular for a lifting platform, comprising; two sets of cross-bars, spaced apart from each other and together forming a first pair of opposite inside bars with upper and lower opposite arms, and a second pair of opposite outside bars with upper and lower opposite arms, the upper arm of each bar engaging the lifting platform and the lower arm of each bar being constructed for abutting a support surface;   a pivot connected to each set of cross-bars for pivotally connecting each set of cross-bars to each other at a location between respective upper and lower arms thereof;   an elastic bellow disposed between the two sets of cross-bars and having opposite end plates;   a pair of cover plates, each engaged over one of the end plates, each cover plate having two opposite flanges adjacent respective arms of the two sets of cross-bars;   two first connecting means mounted coaxially to and diametrically from each other, each of the first connecting means being spaced from the pivot and being connected to one opposite arm of the pair of inside bars for rotatably connecting the inside bars to the outside opposite flanges of one of the cover plates;   two second connecting means mounted coaxially to and diametrically from each other, each second connecting means being spaced from the pivot and being connected to one opposite arm of the pair of outside bars, on inside surfaces of the outside bars, for rotatably connecting the outside bars to the outside opposite flanges of the other cover plate;   each end plate having a centroid, a common axis of the two first connecting means and a common axis of the two second connecting means intersecting a line extending between the centroids of the end plates;   a space between the bars of each set of cross-bars being sufficiently large to receive the flanges which are connected to the outside bars so that the flanges that are connected to the outside bars pass between the bars of each set of cross-bars when the elastic bellow is in a collapsed position with the cover plates near each other.   
     
     
       2. A scissors-type jack mechanism according to claim 1, wherein a distance between the cover plates and the common axis of the connecting means is equal to a height of the elastic bellow in its collapsed position. 
     
     
       3. A scissors-type jack mechanism according to claim 1, wherein the flanges connected to the inside bars are connected to inside surfaces of the inside bars, the distance between the flanges connected to the inside bars being less than the distance between the flanges connected to the outside bars so that with the cover plates near each other, the flanges of the two cover plates overlap each other.